重置样式就是一组CSS声明，用来覆盖不同浏览器渲染HTML元素时的各种默认样式。重置样式一般会被加入到主样式文件的开头，用来将各个浏览器的自有默认样式重置成统一表现，确保样式表中后续追加的样式在不同浏览器中有相同的显示效果。世界上没有完美的重置样式，许多开发者都有自己的一套。以下是Eric Merer的原版（http://meyerweb.com/eric/tools/css/reset/）:
CSS Tools: Reset CSS
The goal of a reset stylesheet is to reduce browser inconsistencies in things like default line heights, margins and font sizes of headings, and so on. The general reasoning behind this was discussed in a May 2007 post, if you're interested. Reset styles quite often appear in CSS frameworks, and the original "meyerweb reset" found its way into Blueprint, among others.
The reset styles given here are intentionally very generic. There isn't any default color or background set for the body element, for example. I don't particularly recommend that you just use this in its unaltered state in your own projects. It should be tweaked, edited, extended, and otherwise tuned to match your specific reset baseline. Fill in your preferred colors for the page, links, and so on.
In other words, this is a starting point, not a self-contained black box of no-touchiness.
If you want to use my reset styles, then feel free! It's all explicitly in the public domain (I have to formally say that or else people ask me about licensing). You can grab a copy of the file to use and tweak as fits you best. If you're more of the copy-and-paste type, or just want an in-page preview of what you'll be getting, here it is.
/* http://meyerweb.com/eric/tools/css/reset/
v2.0 | 20110126
License: none (public domain)
*/ html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section {
display: block;
}
body {
line-height: 1;
}
ol, ul {
list-style: none;
}
blockquote, q {
quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
content: '';
content: none;
}
table {
border-collapse: collapse;
border-spacing: 0;
}
=====================================================================
针对HTML5文档有更好的重置样式选择：如normalize.css (http://necolas.github.com/normalize.css/)
/*! normalize.css v3.0.2 | MIT License | git.io/normalize */ /**
* 1. Set default font family to sans-serif.
* 2. Prevent iOS text size adjust after orientation change, without disabling
* user zoom.
*/ html {
font-family: sans-serif; /* 1 */
-ms-text-size-adjust: 100%; /* 2 */
-webkit-text-size-adjust: 100%; /* 2 */
} /**
* Remove default margin.
*/ body {
margin: 0;
} /* HTML5 display definitions
========================================================================== */ /**
* Correct `block` display not defined for any HTML5 element in IE 8/9.
* Correct `block` display not defined for `details` or `summary` in IE 10/11
* and Firefox.
* Correct `block` display not defined for `main` in IE 11.
*/ article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
main,
menu,
nav,
section,
summary {
display: block;
} /**
* 1. Correct `inline-block` display not defined in IE 8/9.
* 2. Normalize vertical alignment of `progress` in Chrome, Firefox, and Opera.
*/ audio,
canvas,
progress,
video {
display: inline-block; /* 1 */
vertical-align: baseline; /* 2 */
} /**
* Prevent modern browsers from displaying `audio` without controls.
* Remove excess height in iOS 5 devices.
*/ audio:not([controls]) {
display: none;
height: 0;
} /**
* Address `[hidden]` styling not present in IE 8/9/10.
* Hide the `template` element in IE 8/9/11, Safari, and Firefox <.
*/ [hidden],
template {
display: none;
} /* Links
========================================================================== */ /**
* Remove the gray background color from active links in IE 10.
*/ a {
background-color: transparent;
} /**
* Improve readability when focused and also mouse hovered in all browsers.
*/ a:active,
a:hover {
outline: 0;
} /* Text-level semantics
========================================================================== */ /**
* Address styling not present in IE 8/9/10/11, Safari, and Chrome.
*/ abbr[title] {
border-bottom: 1px dotted;
} /**
* Address style set to `bolder` in Firefox 4+, Safari, and Chrome.
*/ b,
strong {
font-weight: bold;
} /**
* Address styling not present in Safari and Chrome.
*/ dfn {
font-style: italic;
} /**
* Address variable `h1` font-size and margin within `section` and `article`
* contexts in Firefox 4+, Safari, and Chrome.
*/ h1 {
font-size: 2em;
margin: 0.67em 0;
} /**
* Address styling not present in IE 8/9.
*/ mark {
background: #ff0;
color: #000;
} /**
* Address inconsistent and variable font size in all browsers.
*/ small {
font-size: 80%;
} /**
* Prevent `sub` and `sup` affecting `line-height` in all browsers.
*/ sub,
sup {
font-size: 75%;
line-height: 0;
position: relative;
vertical-align: baseline;
} sup {
top: -0.5em;
} sub {
bottom: -0.25em;
} /* Embedded content
========================================================================== */ /**
* Remove border when inside `a` element in IE 8/9/10.
*/ img {
border: 0;
} /**
* Correct overflow not hidden in IE 9/10/11.
*/ svg:not(:root) {
overflow: hidden;
} /* Grouping content
========================================================================== */ /**
* Address margin not present in IE 8/9 and Safari.
*/ figure {
margin: 1em 40px;
} /**
* Address differences between Firefox and other browsers.
*/ hr {
-moz-box-sizing: content-box;
box-sizing: content-box;
height: 0;
} /**
* Contain overflow in all browsers.
*/ pre {
overflow: auto;
} /**
* Address odd `em`-unit font size rendering in all browsers.
*/ code,
kbd,
pre,
samp {
font-family: monospace, monospace;
font-size: 1em;
} /* Forms
========================================================================== */ /**
* Known limitation: by default, Chrome and Safari on OS X allow very limited
* styling of `select`, unless a `border` property is set.
*/ /**
* 1. Correct color not being inherited.
* Known issue: affects color of disabled elements.
* 2. Correct font properties not being inherited.
* 3. Address margins set differently in Firefox 4+, Safari, and Chrome.
*/ button,
input,
optgroup,
select,
textarea {
color: inherit; /* 1 */
font: inherit; /* 2 */
margin: 0; /* 3 */
} /**
* Address `overflow` set to `hidden` in IE 8/9/10/11.
*/ button {
overflow: visible;
} /**
* Address inconsistent `text-transform` inheritance for `button` and `select`.
* All other form control elements do not inherit `text-transform` values.
* Correct `button` style inheritance in Firefox, IE 8/9/10/11, and Opera.
* Correct `select` style inheritance in Firefox.
*/ button,
select {
text-transform: none;
} /**
* 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio`
* and `video` controls.
* 2. Correct inability to style clickable `input` types in iOS.
* 3. Improve usability and consistency of cursor style between image-type
* `input` and others.
*/ button,
html input[type="button"], /* 1 */
input[type="reset"],
input[type="submit"] {
-webkit-appearance: button; /* 2 */
cursor: pointer; /* 3 */
} /**
* Re-set default cursor for disabled elements.
*/ button[disabled],
html input[disabled] {
cursor: default;
} /**
* Remove inner padding and border in Firefox 4+.
*/ button::-moz-focus-inner,
input::-moz-focus-inner {
border: 0;
padding: 0;
} /**
* Address Firefox 4+ setting `line-height` on `input` using `!important` in
* the UA stylesheet.
*/ input {
line-height: normal;
} /**
* It's recommended that you don't attempt to style these elements.
* Firefox's implementation doesn't respect box-sizing, padding, or width.
*
* 1. Address box sizing set to `content-box` in IE 8/9/10.
* 2. Remove excess padding in IE 8/9/10.
*/ input[type="checkbox"],
input[type="radio"] {
box-sizing: border-box; /* 1 */
padding: 0; /* 2 */
} /**
* Fix the cursor style for Chrome's increment/decrement buttons. For certain
* `font-size` values of the `input`, it causes the cursor style of the
* decrement button to change from `default` to `text`.
*/ input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
height: auto;
} /**
* 1. Address `appearance` set to `searchfield` in Safari and Chrome.
* 2. Address `box-sizing` set to `border-box` in Safari and Chrome
* (include `-moz` to future-proof).
*/ input[type="search"] {
-webkit-appearance: textfield; /* 1 */
-moz-box-sizing: content-box;
-webkit-box-sizing: content-box; /* 2 */
box-sizing: content-box;
} /**
* Remove inner padding and search cancel button in Safari and Chrome on OS X.
* Safari (but not Chrome) clips the cancel button when the search input has
* padding (and `textfield` appearance).
*/ input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
-webkit-appearance: none;
} /**
* Define consistent border, margin, and padding.
*/ fieldset {
border: 1px solid #c0c0c0;
margin: 0 2px;
padding: 0.35em 0.625em 0.75em;
} /**
* 1. Correct `color` not being inherited in IE 8/9/10/11.
* 2. Remove padding so people aren't caught out if they zero out fieldsets.
*/ legend {
border: 0; /* 1 */
padding: 0; /* 2 */
} /**
* Remove default vertical scrollbar in IE 8/9/10/11.
*/ textarea {
overflow: auto;
} /**
* Don't inherit the `font-weight` (applied by a rule above).
* NOTE: the default cannot safely be changed in Chrome and Safari on OS X.
*/ optgroup {
font-weight: bold;
} /* Tables
========================================================================== */ /**
* Remove most spacing between table cells.
*/ table {
border-collapse: collapse;
border-spacing: 0;
} td,
th {
padding: 0;
}